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Unformatted text preview: NST 160 Dietary Carbohydrates Marc K. Hellerstein, M.D., Ph.D. Professor of Human Nutrition (D.H. Calloway Chair), University of California Berkeley; Professor of Endocrinology, Metabolism and Nutrition, Dept. of Medicine, University of California at San Francisco I) Carbohydrate (CHO) is a macronutrient- definition II) Functions of CHOs in the body III What do people eat? CHO in the die Outline III) What do people eat? CHO in the diet IV) Types of CHOs V) Diseases of CHO utilization VI) Health impact of different CHO intake – Macronutrients refer to the classes of foods ingested in large quantity that provide bulk energy – There are 3 major chemical classes of macronutrients: carbohydrates, fats and proteins Carbohydrate is a Macronutrient – Each class of macronutrient has very different pathways of metabolism, functions, and storage levels in the body – Many popular dietary interventions focus on manipulating the relative content of macronutrients in the diet – CHOs are used by essentially all tissues – A CHO (glucose) is exclusive energy source for some tissues – Most important is brain – Also red blood cells – Glucose can be taken up from blood or Use of CHOs for Energy by the Body – Glucose can be taken up from blood or mobilized from stores (glycogen) – Galactose (from lactose in breast milk) is important to infants : goes to liver for assimilation – Fructose is also efficiently used (by liver only) – Stored in muscle, liver and other tissues – Stored as complex CHO in tissues (called glycogen) – Key concept: limited storage capacity for CHO in the body – Total <500g = 2,000 Calories: < 1 day energy needs! Storage of CHO in the Body – Compare to fat stores in the body – Typically 15 Kg fat = 135,000 Calories – Why limited CHO storage capacity? – Low energy density- we would weigh 100s of Kg more! – Significance: we usually burn what CHO we eat every day – Body can convert CHO to fat – Process is called de novo lipogenesis – Very active in some organisms – e.g., Grain-fed cows or pigs; mice on high CHO diet Conversion of CHO to fat – Plants and algae (basis of biofuels!!) – Occurs in liver and fat cells (adipose) – Not very active in most human beings under most dietary circumstances, however – Therefore, most dietary CHO is used for energy or stored as glycogen in tissues – Anaerobic energy extraction – Occurs when there in not enough oxygen for tissues energy needs – Example: sprint or power exercise by muscle – CHOs can provide shor term energy by Special Functions of CHOs in Energy Economy of the Body – CHOs can provide short-term energy by process of glycolysis, w/out oxygen...
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